function printPoint(sel,content,point) {
	updateSpan(sel, content+"坐标为:(" + point.x + "," + point.y + ")");
}

function printNearPoint(points) {
	var content = '';
	for(let i = 0; i < points.length; i++) {
		content += "(" + points[i].x + "," + points[i].y + ")距离：" + points[i].d + "、";
	}
	updateSpan('#nPoint', "起点最近的四个信号器的坐标为:" + content);
}